Multilinguals are impressive masters of flexibility. They can speak in only one language at a time without any apparent trouble, but also switch their languages easily if necessary. This apparent paradox has led researchers to ask whether multilinguals’ knowledge of their languages – such as the knowledge of words – is stored and accessed separately or together. This chapter summarizes what we currently know about the structure and workings of the tri- and multilingual lexicon, reviewing findings for word recognition, word production, and translation, as well as evidence from neurocognitive studies. It shows that the answer to the question how the trilingual mental lexicon is organized is not a simple, black-or-white one (i.e., ‘integrated’ or ‘separate’). Rather, the available evidence supports a nuanced view of trilingual word processing that is co-determined by characteristics of the individual and their acquisition history, the properties of the involved languages, and the nature of the task.